Index: clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp
===================================================================
--- clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp
+++ clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp
@@ -42,7 +42,7 @@
   // Return that this method is unsupported.
   writeMessage(
       R"({"jsonrpc":"2.0","id":)" + ID +
-      R"(,"error":{"code":-32601}})");
+      R"(,"error":{"code":-32601,"message":"method not found"}})");
 }
 
 void Handler::handleNotification(llvm::yaml::MappingNode *Params) {
Index: clang-tools-extra/trunk/test/clangd/unsupported-method.test
===================================================================
--- clang-tools-extra/trunk/test/clangd/unsupported-method.test
+++ clang-tools-extra/trunk/test/clangd/unsupported-method.test
@@ -0,0 +1,19 @@
+# RUN: clangd -run-synchronously < %s | FileCheck %s
+# It is absolutely vital that this file has CRLF line endings.
+#
+Content-Length: 125
+
+{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
+
+Content-Length: 143
+
+{"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"file:///main.cpp","languageId":"cpp","version":1,"text":""}}}
+
+Content-Length: 92
+
+{"jsonrpc":"2.0","id":1,"method":"textDocument/jumpInTheAirLikeYouJustDontCare","params":{}}
+# CHECK: {"jsonrpc":"2.0","id":1,"error":{"code":-32601,"message":"method not found"}}
+
+Content-Length: 44
+
+{"jsonrpc":"2.0","id":2,"method":"shutdown"}